package 快乐数;

class Solution {
    private int bitSum(int n){
        int sum = 0;
        while (n != 0){
            int t = n % 10;
            sum += t * t;
            n /= 10;
        }
        return sum;
    }
    public boolean isHappy(int n) {
        int slow = n;
        int fast = bitSum(n);
        while (fast != slow){
            slow = bitSum(slow);
            fast = bitSum(bitSum(fast));
        }
        return fast == 1;
    }
}